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Year 13 biology coursework experiments

Year 13 biology coursework experiments
Year 13 biology coursework experiments
Year 13 biology coursework experiments
Year 13 biology coursework experiments
Tuesday 1st September 2015 by C. Freeman

Our Sixth Formers have been completing experiments as part of their A Level biology syllabus. Their research has included investigating the effects of insecticide, neutralising nettle stings and measuring the effects of fruit enzymes. The students have had to design their own experiments, do test studies and then take detailed readings over the course of a few days. They will write up their findings in detailed reports, along with the conclusions of their study.

Kai Chan was looking at formic acid, which is the irritant in stinging nettles. Although he extracted some he wasn’t able to get enough for the entire experiment and so he substituted methanoic acid which has similar properties. He tested a variety of substances, including cucumber, tomatoes, bicarbonate of soda, avocados, toothpaste, celery and washing powder to see which were the best at neutralising the acid, thus relieving the pain. He said: ‘I haven’t been stung by stinging nettles until now but everyone I know has been. I was wondering why it hurts so much and wanted to investigate more. I am going to turn the acid into a solution and will see which substance is the best at neutralising it.

‘It is too early to say which will give the best results but tomatoes should be really good as the skin is quite acidic however apparently when it is consumed it turns to alkali in your blood. The only problem I have encountered was when the formic acid from the stinging nettles was dark green – like a ph 9 colour and when I tried to use universal indicator on it then you couldn’t tell when it changes from acid to neutral so I had to use other test methods including a pH probe.’

Leanne Tough tested the effect of insecticide on woodlice behaviour and their response to light. She said: ‘I decided to do this after hearing about how pesticides are affecting bees and I wanted to test to see whether other creatures show a similar response. I have been putting individual woodlice in a prepared dish with soil and a common household pesticide and timing their responses over half an hour to see whether the pesticide has an effect. Also they naturally like to be in the dark so I also put a blacked out section in the dish to see whether they shelter under it to gauge whether the insecticide affects their natural behaviour.’

Sam Lewin was researching to see whether barley straw can increase the clarity of water. He said: ‘As barley straw decomposes it is meant to release chemicals to prevent green algae from growing so I am investigating that. I have got samples of contaminated pond water and I put a different amount of barley straw in each one. The control pot has none in and then I have put a couple of grams in one and three grams in the other. Over the course of a couple of weeks I am going to be measuring the clarity of the water using coloured charts and matching the samples with numbered examples. I am expecting that as the mass of barley straw is increased then the water will clear more quickly.’

Lydia Thompson O’Connor is investigating the change in enzyme activity when fruit ripens. She said: ‘I am using wallpaper paste as it has cellulose in it like the cell walls of a plant. I then add pureed fruit and the enzymes in the fruit extract break down the cellulose. As the enzyme activity increases then the sample becomes thinner. I time how long it takes to come out of the syringe, then I put it in a water bath for half an hour and test it again. It should take less time as the sample should be less viscous as being in a water bath at 30 degree should speed up the reaction. For my pilot study I tried raspberries, tomatoes, avocado and apples to see which extract would work best. I found that tomatoes performed the best so I am just doing this series of experiments with tomatoes. It is quite messy but the results are turning out as expected.'

Mrs Hegarty oversaw the students’ work. She said: ‘This year they have been amazingly well organised and they are just getting on with it, troubleshooting where necessary and self managing really well, which is excellent. They will have the rest of this term to get all of their sections of the report completed and handed in as a final draft at the end of this term.’

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